Hiqa Inspectors say hygiene standards at the National Maternity Hospital's delivery ward are very poor.
In an unannounced inspection of Holles Street hospital last November they found evidence of organic contamination on surfaces, including equipment.
In a new report published this morning Hiqa says management said high levels of activity recently had made it difficult to access the delivery ward for cleaning.
However, inspectors disputed this.
Concern has also been raised about the storage of syringes, and medicines being left out for long periods of time.
In a statement this afternoon (3.35pm) the National Maternity Hospital says that they have already addressed some of these issues - but it's difficult to deep clean when rooms are rarely vacant.